code: def test_gauge(start_prometheus_http_server):
      g = Gauge("test_gauge", "A test gauge")
      assert g.name == "test_gauge"
      assert g.description == "A test gauge"
      assert set(["host", "pid"]).issubset(set(g.tag_keys))
      assert g.type == "Gauge"
      g.record(0.1)
      verify_metric("test_gauge", 0.1)
      g.record(1.1)
      verify_metric("test_gauge", 1.1)
  
file_path: mars/mars/metrics/backends/prometheus/tests/test_prometheus_metric.py
imports: import pytest
  import time
  from .....utils import get_next_port
  from ..prometheus_metric import Counter, Gauge, Histogram, Meter
label_desc: Use image node_id 4 for calling a global function with example usage: test_gauge(start_prometheus_http_server) without return types